<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <input type="text" />
  <script>
    var ipt = document.querySelector('input')
    ipt.onkeyup = function (e) {
      // String.fromCharCode：将数值转换为字母
      var n = String.fromCharCode(e.keyCode)
      console.log(e.keyCode, n)
    }
  </script>
</body>

</html>